The presence of algae in both surface and wastewater is one of the main causes of water quality deterioration (Al-Zboon and Al-Suhaili, 2009; Rodrigues et al., 2011). Algal growth in different parts of conventional wastewater treatment plants or aerated lagoon systems can result in false indications in the final effluent parameters, such as TSS, CBOD5 and COD (Heng et al., 2010; Chow et al., 1999; Gitzgerald, 1964). In surface water, the presence of algae creates nuisance surface scum, poor water clarity, and noxious odours (Abdel-Raouf et al., 2012; Aly and Sami, 2014). If this surface water is used to produce drinking water, the algae may lead to problems in the drinking water treatment process, such as reduced filter runs and an increase in the amount of disinfectant needed, which can increase the cost of the treatment (Horan, 1990).
In order to set up an efficient control and treatment process to minimize algal concentration in water samples, it is necessary to have access to a concentration measurement method which is quick, simple, and accurate, and which can detect low algal concentrations in different types of water. The methods currently used to determine algal concentration in different water samples include algal number, as prescribed in the Standard Methods for the Examination of Water and Wastewater (APHA, 1985), and the determination of chlorophyll extract concentration in relation to total algal concentration (Wasmund et al., 2006; Jones and Lee, 1982). Both of these methods are labour and time intensive, expensive, and require extensive laboratory preparation. Moreover, it is not clear how efficient the chlorophyll extraction process is or how its results are related to the real algal concentration in water solutions.
Recently, the use of real-time and inline spectrophotometric methods at water and wastewater treatment plants to measure different parameters, such as total organic carbon, disinfection by-product precursors, nitrates, and UV transmittance for UV disinfection have increased dramatically (James et al., 2003; Langergraber et al., 2004; Gibbons and Örmeci, 2013; Al Momani and Ormeci, 2014). These measurements are considered practical, quick, simple, and accurate for these industries.
Different studies have reported that the absorbance measurements of algae in water produce a spectrum with a maximum absorbance near the wavelength of red light (540-690 nm) (Gaigalas et al., 2009; UGWU et al., 2007; Liang et al., 2009; Sung et al., 2010). In some types of water and wastewater, the accuracy of the spectrophotometric measurements is affected by water turbidity and by the presence of other constituents in the water sample that mask the absorbance response or produce high levels of noise in the spectral background.
Spectral first and higher-order derivatives have been used by different studies to facilitate the location of the critical wavelength, to reduce low-frequency background noise, and to resolve overlapping spectra (Demetriades-Shah et al., 1990). However, it appears that no research work has explored the use of the first derivative of the absorbance spectra to determine the concentration of algae in an aqueous solution.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.